Processes for making ethylene glycol and/or propylene glycol from aldose- and/or ketose-yielding carbohydrates with integrated tungsten catalyst recovery

ABSTRACT

Integrated processes are disclosed for the catalytic conversion of carbohydrate to ethylene glycol and/or propylene glycol using a homogeneous, tungsten-containing retro-aldol catalyst. In these processes, the carbohydrate is subjected to retro-aldol conversion and hydrogenation to provide a reaction product containing ethylene glycol and/or propylene glycol, other reaction process including organic acids, itols and tungsten species. Ethylene glycol and propylene glycol are separated from the reaction product for purification, and at least a portion of the remaining fraction is subjected to ion exclusion chromatography to provide an eluant containing tungsten species and a subsequent eluant containing organic acids and a substantially reduced concentration of tungsten species. At least a portion of the eluant containing tungsten species can be recycled for reuse directly or with intervening unit operations to enhance the catalytic activity of the tungsten species. The organic-containing fraction can be subjected to one or more unit operations to provide salable products or subjected to selective hydrogenolysis to lower glycols.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to U.S. Provisional Application No.63/300,696, filed Jan. 19, 2022 and entitled “PROCESSES FOR MAKINGETHYLENE GLYCOL AND/OR PROPYLENE GLYCOL FROM ALDOSE- AND/ORKETOSE-YIELDING CARBOHYDRATES WITH INTEGRATED TUNGSTEN CATALYSTRECOVERY,” which is hereby incorporated by reference in its entiretyunder 35 U.S.C. §119(e).

FIELD OF THE INVENTION

This invention pertains to processes for the catalytic production ofethylene glycol and/or propylene glycol from aldose- and/orketose-yielding carbohydrates, particularly processes that haveintegrated tungsten catalyst recovery.

BACKGROUND

Ethylene glycol and propylene glycol are valuable commodity chemicals,and each has a broad range of uses. These chemicals are currently madefrom starting materials based upon fossil hydrocarbons (petrochemicalroutes).

Proposals have been made to manufacture ethylene glycol and propyleneglycol from renewable resources such as carbohydrates, e.g., sugars. Onesuch route has been practiced commercially and involves the fermentationof sugars to ethanol, catalytically dehydrogenating the ethanol toethylene and the ethylene is then catalytically converted to ethyleneoxide which can then be reacted with water to produce ethylene glycol.This route is not economically attractive as three conversion steps arerequired, and it suffers from conversion efficiency losses. Forinstance, the theoretical yield of ethanol is 0.51 grams per gram ofsugar with, on a theoretical basis, one mole of carbon dioxide beinggenerated per mole of ethanol.

Alternative processes to make ethylene glycol and propylene glycol fromrenewable resources are thus sought. These alternative processes includecatalytic routes such as hydrogenolysis of sugar and a two-catalystprocess using a retro-aldol catalyst (“retro-aldol route”) to generateintermediates from sugar that can be hydrogenated over a hydrogenationcatalyst to produce ethylene glycol and propylene glycol.

In the retro-aldol route, the carbohydrate is converted over aretro-aldol catalyst to intermediates, and the intermediates are thencatalytically converted over a hydrogenation catalyst (“Hcat”) toethylene glycol and/or propylene glycol. The sought initially-occurringretro-aldol reaction is endothermic and requires a high temperature,e.g., often over 230° C., to provide a sufficient reaction rate topreferentially favor the conversion of carbohydrate to intermediatesover the hydrogenation of carbohydrate to polyol such as sorbitol.

Catalysts used for the retro-aldol conversion are typically homogeneousand comprise tungsten and thus exit the reaction system with theproduct. Various proposals have been made to separate the monoethyleneglycol and propylene glycol from the effluent of the reactor and recycleat least a portion of the remainder which contains tungsten to thereactor. See, for instance, U.S. Pat. Nos. 10,294,181 and 10,647,646 andU.S. Pat. Application Publication 2021/0087128. While a recycle canconserve tungsten, tungsten species can form during use that arecatalytically inactive or have reduced or undesirable catalyticactivities.

Tungsten can also be recovered, e.g., by ion exchange or precipitation,and the recovered tungsten can be converted to catalytically activespecies for retro-aldol conversions. See, U.S. Pat. ApplicationPublication 2021/0087128.

Processes for making lower glycols from carbohydrates via theretro-aldol process are sought to recover tungsten compound fromprocess, including purge, streams, which processes are easily operated,require little energy and provide recovered tungsten compound that hasdesirable catalytic activity for retro-aldol conversions.

SUMMARY

The processes of this invention involve an energy efficient andefficacious method for recovering tungsten from processes for makinglower glycols from carbohydrates via the retro-aldol process. Theprocesses involve the integration of ion-exclusion chromatography forthe selective recovery of tungsten compounds, and if desired, recycle oftungsten compounds, while providing a higher boiling organic phase thatcan, if desired, be subjected to hydrogenolysis to enhance theconversion of carbohydrate to lower glycol.

By this invention integrated processes are provided for the catalyticconversion of carbohydrate to ethylene glycol and/or propylene glycolusing a homogeneous, tungsten-containing retro-aldol catalyst. In theseprocesses, the carbohydrate is subjected to retro-aldol conversion andhydrogenation to provide a reaction product containing ethylene glycoland/or propylene glycol, other reaction process including organic acids,itols and tungsten species. Ethylene glycol and propylene glycol areseparated from the reaction product for purification, and at least aportion of the remaining fraction (“retained fraction”) is subjected toion exclusion chromatography to provide an eluant containing tungstenspecies and a subsequent eluant containing organic acids and asubstantially reduced concentration of tungsten species. At least aportion of the eluant containing tungsten species can be recycled forreuse directly or with intervening unit operations to enhance thecatalytic activity of the tungsten species.

It has been found that despite the tungsten species being a very smallportion of the retained fraction, a significant portion of the tungsten,often at least about 60, and sometimes more than about 70 or 80, percent(based on atomic tungsten) can be recovered by ion exclusionchromatography with at least 90 percent by mass of the organics beingseparated into the subsequent eluant phase. Thus, thetungsten-containing eluent is suitable for recycle without unduebuild-up of non-reactive organics in the reaction zone, and anyintervening treatments of the tungsten species in the eluant to berecycled involve the treatment of a reduce volume of liquid. And, withan intervening treatment such as pH adjustment, the reduced content oforganic acids results in less pH adjustment agent being required for adesired pH change to convert the tungsten compounds to those desired forrecycle.

In accordance with this invention, catalytic processes are provided forproducing a lower glycol comprising at least one of ethylene glycol andpropylene glycol from a carbohydrate-containing feed that comprises atleast one of aldose- and ketose-yielding carbohydrate, which processescomprise:

-   (a) continuously or intermittently supplying the feed to a reaction    zone having therein dissolved tungsten compounds at least one of    which is homogeneous, tungsten-containing retro-aldol catalyst and    at least one heterogeneous hydrogenation catalyst, said liquid    medium being at catalytic conversion conditions including the    presence of dissolved hydrogen, to produce a reaction product    containing said lower glycol and one or more higher boiling point    coproducts comprising sorbitol, erythritol, threitol and glycerin;-   (b) continuously or intermittently withdrawing liquid medium that    contains reaction product and dissolved tungsten compounds from the    reaction zone;-   (c) subjecting at least a portion of the withdrawn liquid medium to    one or more unit operations to remove at least a portion of the    lower glycol in a separated fraction and provide a retained liquid    phase containing dissolved tungsten compounds and higher boiling    point coproducts with a mass ratio of higher boiling coproducts to    tungsten compounds calculated as the metal of greater than about    4:1; and-   (d) contacting at least a portion of the retained liquid phase with    an ionic resin for ion exclusion chromatography, to provide a first    eluted fraction containing dissolved tungsten compounds and a mass    ratio of higher boiling coproducts to tungsten compounds calculated    as the metal of less than about 5:1,preferably less than about 1:1,    and contacting the ionic resin with sufficient solvent to provide at    least one subsequent eluted fraction containing one or more higher    boiling point coproducts and a lower concentration of tungsten    (calculated as the metal) than that of the retained liquid phase,    often less than about 10 parts by mass of tungsten compounds    calculated as the metal per 100 parts by mass of higher boiling    coproducts.

In preferred processes of this invention, at least about 90 mass percentof the tungsten compounds contained in the retained liquid phasecontacted with the ion exchange resin are in the first eluted fraction.Preferably, at least a portion of the first eluted fraction is recycledto step (a), and in some instances, the first eluted fraction isprovided at a pH of from about 6.5 to 8 before being passed to step (a).In some instances at least a portion of the tungsten compounds in therecycled, first eluted fraction is half neutralized tungstic acid. Ifdesired, the subsequent eluted fraction is subjected to hydrogenolysisconditions to convert itols to lower glycol.

This invention also pertains to producer composition of mattercomprising dissolved tungsten compound and one or more higher boilingpoint polyols comprising sorbitol, erythritol, threitol and glycerinwherein the mass ratio of total higher boiling polyol to tungstencompounds calculated as the metal is less than about 5:1, preferablyless than about 1:1 and sometimes between about 0.01:1 and 1:1.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic diagram of an apparatus for practicing theprocesses of this invention.

DETAILED DISCUSSION

All patents, published patent applications and articles referencedherein are hereby incorporated by reference in their entirety.

Definitions

As used herein, the following terms have the meanings set forth belowunless otherwise stated or clear from the context of their use.

Where ranges are used herein, the end points only of the ranges arestated so as to avoid having to set out at length and describe each andevery value included in the range. Any appropriate intermediate valueand range between the recited endpoints can be selected. By way ofexample, if a range of between 0.1 and 1.0 is recited, all intermediatevalues (e.g., 0.2, 0.3. 0.63, 0.815 and so forth) are included as areall intermediate ranges (e.g., 0.2-0.5, 0.54-0.913, and so forth).

The use of the terms “a” and “an” is intended to include one or more ofthe element described.

Admixing or admixed means the formation of a physical combination of twoor more elements which may have a uniform or non-uniform compositionthroughout and includes, but is not limited to, solid mixtures,solutions and suspensions.

Aldose means a monosaccharide that contains only a single aldehyde group(—CH═O) per molecule and having the generic chemical formulaC_(n)(H₂O)_(n). Non-limiting examples of aldoses include aldohexose (allsix-carbon, aldehyde-containing sugars, including glucose, mannose,galactose, allose, altrose, idose, talose, and gulose); aldopentose (allfive-carbon aldehyde containing sugars, including xylose, lyxose,ribose, and arabinose); aldotetrose (all four-carbon, aldehydecontaining sugars, including erythrose and threose) and aldotriose (allthree-carbon aldehyde containing sugars, including glyceraldehyde).

Aldose-yielding carbohydrate means an aldose or a di- or polysaccharidethat can yield aldose upon hydrolysis. Sucrose, for example, is analdose-yielding carbohydrate even though it also yields ketose uponhydrolysis.

Aqueous and aqueous medium or solution mean that water is present butdoes not require that water be the predominant component. For purposesof illustration and not in limitation, a solution of 90 volume percentof ethylene glycol and 10 volume percent water would be an aqueoussolution. Aqueous solutions include liquid media containing dissolved ordispersed components such as, but not in limitation, colloidalsuspensions and slurries.

Bio-sourced carbohydrate feedstock means a product that includescarbohydrates sourced, derived or synthesized from, in whole or insignificant part, to biological products or renewable agriculturalmaterials (including, but not limited to, plant, animal and marinematerials) or forestry materials.

Calculated as the metal means calculation as elemental metal regardlessof the molecular structure of the metal-containing compound.

Catalyst for converting the carbohydrate means one or more catalysts toeffect the catalytic conversion which would both the retro-aldolcatalyst and the hydrogenation catalyst (“Hcat”), each of which cancomprise one or a mixture of catalysts. The catalyst can contain one ormore catalytic metals, and for Hcats, include supports, binders andother adjuvants. Catalytic metals are metals that are in their elementalstate or are ionic or covalently bonded. The term catalytic metalsrefers to metals that are not necessarily in a catalytically activestate, but when not in a catalytically active state, have the potentialto become catalytically active. Catalytic metals can provide catalyticactivity or modify catalytic activity such as promotors, selectivitymodifiers, and the like.

Commencing contact means that a fluid starts a contact with a component,e.g., a medium containing a homogeneous catalyst or heterogeneouscatalyst, e.g., Heat, but does not require that all molecules of thatfluid contact the catalyst.

Compositions of aqueous solutions are determined using gaschromatography for lower boiling components, usually components having 3or fewer carbons and a normal boiling point less than about 300° C., andhigh performance liquid chromatography for higher boiling components,usually 3 or more carbons, and those components that are thermallyunstable.

Conversion efficiency of aldohexose to ethylene glycol is reported inmass percent and is calculated as the mass of ethylene glycol containedin the product solution divided by the mass of aldohexose theoreticallyprovided by the carbohydrate feed and thus includes any aldohexose perse contained in the carbohydrate feed and the aldohexose theoreticallygenerated upon hydrolysis of any di- or polysaccharide contained in thecarbohydrate feed.

Hexitol means a six carbon compound having the empirical formula ofC₆H₁₄O₆ with one hydroxyl per carbon.

High shear mixing involves providing a fluid traveling at a differentvelocity relative to an adjacent area which can be achieved throughstationary or moving mechanical means to effect a shear to promotemixing. As used herein, the components being subjected to high shearmixing may be immiscible, partially immiscible or miscible.

Hydraulic distribution means the distribution of an aqueous solution ina vessel including contact with any catalyst contained therein.

Immediately prior to means no intervening unit operation requiring aresidence time of more than one minute exists.

Intermittently means from time to time and may be at regular orirregular time intervals.

Ion exclusion chromatography involves an adsorbent material that issaturated with the same mobile ions (cationic or anionic) as are presentin the feed, and because it is saturated, similar ions are repelled bythe adsorbent material. Ion exclusion chromatography can use ionexchange resins beds acting as a charged solid separation medium. Theion exclusion chromatographic techniques using porous resin beds canserve to effect size exclusion separations such that molecules can beseparated by size and molecular weight with larger and heavier moleculesbeing eluted first.

Itol means a carbon compound containing at least two hydroxyl groupswith one hydroxyl on each carbon atom.

Ketose means a monosaccharide containing one ketone group per molecule.Non-limiting examples of ketoses include ketohexose (all six-carbon,ketone-containing sugars, including fructose, psicose, sorbose, andtagatose), ketopentose (all five-carbon ketone containing sugars,including xylulose and ribulose), ketotetrose (all four-carbon, ketosecontaining sugars, including erythrulose), and ketotriose (allthree-carbon ketose containing sugars, including dihydroxyacetone).

Ketose-yielding carbohydrate means a ketose or a di- or polysaccharideor hemicellulose that can yield ketose or ketose precursor uponhydrolysis. Most sugars are ring structures under ambient conditions andthus the ketose form occurs under the conditions of the process of thisinvention. Sucrose, for example, is a ketose-yielding carbohydrate eventhough it also yields aldose upon hydrolysis. For purposes herein,carbohydrates that produce both aldose and ketose will be deemedketose-yielding carbohydrate except as the context requires otherwise.

Liquid medium means the liquid in the reactor. The liquid is a solventfor the carbohydrate, intermediates and products and for thehomogeneous, tungsten-containing retro-aldol catalyst. Typically andpreferably, the liquid contains at least some water and is thus termedan aqueous medium.

Lower glycol is ethylene glycol or propylene glycol or mixtures thereof.

The pH of an aqueous solution is determined at ambient pressure andtemperature. In determining the pH of, for example the aqueous,hydrogenation medium or the product solution, the liquid is cooled andallowed to reside at ambient pressure and temperature for 2 hours beforedetermination of the pH. Where the aqueous solution contains less thanabout 50 mass percent water, e.g., in a glycol-rich medium, water isadded to a sample to provide a solution containing about 50 mass percentwater. For purposes of consistency, the dilution of solutions is to thesame mass percent water.

pH control agents means one or more of buffers and acids or bases.

A pressure sufficient to maintain at least partial hydration of acarbohydrate means that the pressure is sufficient to maintainsufficient water of hydration on the carbohydrate to retardcaramelization. At temperatures above the boiling point of water, thepressure is sufficient to enable the water of hydration to be retainedon the carbohydrate.

A rapid diffusional mixing is mixing where at least one of the two ormore fluids to be mixed is finely divided to facilitate mass transfer toform a substantially uniform composition.

A reactor can be one or more vessels in series or in parallel and avessel can contain one or more zones. A reactor can be of any suitabledesign for continuous operation including, but not limited to, tanks andpipe or tubular reactor and can have, if desired, fluid mixingcapabilities. Types of reactors include, but are not limited to, laminarflow reactors, fixed bed reactors, slurry reactors, fluidized bedreactors, moving bed reactors, simulated moving bed reactors,trickle-bed reactors, bubble column and loop reactors.

Separation unit operations are one or more operations to selectivelyseparate chemicals, including, but not limited to, chromatographicseparation, sorption, membrane separation, flash separation,distillation, rectification, and evaporation.

Soluble means able to form a single liquid phase or to form a colloidalsuspension.

Solubilized tungsten compounds are dissolved tungsten compounds orcolloidally suspended tungsten compounds in the reaction medium.

Vapor/liquid separation is a separation providing one or more vaporstreams and one or more liquid streams and can be based uponchromatographic separation, cyclic sorption, membrane separation, flashseparation, distillation, rectification, and evaporation (e.g., thinfilm evaporators, falling film evaporators and wiped film evaporators).

Carbohydrate Feed

The processes of this invention use a carbohydrate feed that contains analdohexose-yielding carbohydrate or ketose-yielding carbohydrate, theformer providing under retro-aldol reaction conditions, an ethyleneglycol-rich product and the latter providing a propylene glycol-richproduct. Where product solutions containing a high mass ratio ofethylene glycol to propylene glycol are sought, the carbohydrate in thefeed comprises at least about 90, preferably at least about 95 or 99,mass percent of aldohexose-yielding carbohydrate. Often the carbohydratefeed comprises a carbohydrate polymer such as starch, cellulose, orpartially to essentially fully hydrolyzed fractions of such polymers ormixtures of the polymers or mixtures of the polymers with partiallyhydrolyzed fractions.

The carbohydrate feed is most often at least one of pentose and hexoseor compounds that yield pentose or hexose. Examples of pentose andhexose include xylose, lyxose, ribose, arabinose, xylulose, ribulose,glucose, mannose, galactose, allose, altrose, idose, talose, and gulosefructose, psicose, sorbose, and tagatose. Most bio-sourced carbohydratefeedstocks yield glucose upon being hydrolyzed. Glucose precursorsinclude, but are not limited to, maltose, trehalose, cellobiose,kojibiose, nigerose, nigerose, isomaltose, β,β-trehalose, α,β-trehalose,sophorose, laminaribiose, gentiobiose, and mannobiose. Carbohydratepolymers and oligomers such as hemicellulose, partially hydrolyzed formsof hemicellulose, disaccharides such as sucrose, lactulose, lactose,turanose, maltulose, palatinose, gentiobiulose, melibiose, andmelibiulose, or combinations thereof may be used.

If desired, the carbohydrate feed can be treated to remove one or moreimpurities, especially impurities that have the potential to affect oneor more of the catalysts. For instance, moieties that can oxidize orsulfide one or more of the catalysts used in the processes.

The carbohydrate feed can be solid or, preferably, in a liquidsuspension or dissolved in a solvent such as water. Where thecarbohydrate feed is in a non-aqueous environment, it is preferred thatthe carbohydrate is at least partially hydrated. Non-aqueous solventsinclude alkanols, diols and polyols, ethers, or other suitable carboncompounds of 1 to 6 carbon atoms. Solvents include mixed solvents,especially mixed solvents containing water and one of the aforementionednon-aqueous solvents. Certain mixed solvents can have higherconcentrations of dissolved hydrogen under the conditions of thehydrogenation reaction and thus reduce the potential for hydrogenstarvation. Preferred non-aqueous solvents are those that can behydrogen donors such as isopropanol. Often these hydrogen donor solventshave the hydroxyl group converted to a carbonyl when donating a hydrogenatom, which carbonyl can be reduced under the conditions in the reactionzone. Most preferably, the carbohydrate feed is provided in an aqueoussolution. In any event, the volume of feed and the volume of raw productwithdrawn need to balance to provide for a continuous process.

Further considerations in providing the carbohydrate to the reactionzone are minimizing energy and capital costs. For instance, in steadystate operation, the solvent contained in the feed exits the reactionzone with the raw products and needs to be separated in order to recoverthe sought glycol products.

Preferably, the feed is introduced into the reaction zone in a mannersuch that undue concentrations of feed that can result in hydrogenstarvation are avoided. With the use of a greater number of multiplelocations for the supply of carbohydrate per unit volume of the reactionzone, the more concentrated the carbohydrate in the feed can be. Ingeneral, the mass ratio of water to carbohydrate in the carbohydratefeed is preferably in the range of 4:1 to 1:4. Aqueous solutions of 600or more grams per liter of certain carbohydrates such as dextrose andsucrose are sometimes commercially available.

In some instances, recycled hydrogenation solution having a substantialabsence of hydrogenation catalyst, or aliquot or separated portionthereof, is added as a component to the carbohydrate feed. The recycledhydrogenation solution can be one or more of a portion of the rawproduct stream or an internal recycle where hydrogenation catalyst isremoved. Suitable solid separation techniques include, but are notlimited to, filtration and density separation such as cyclones, vaneseparators, and centrifugation. With this recycle, the amount of freshsolvent for the feed is reduced, yet the carbohydrate is fed at a ratesufficient to maintain a high conversion per unit volume of reactionzone. The use of a recycle, especially where the recycle is an aliquotportion of the raw product stream, enables the supply of lowconcentrations of carbohydrate to the reaction zone while maintaining ahigh conversion of carbohydrate to ethylene glycol. Additionally, it isfeasible to maintain the recycle stream at or near the temperature inthe reaction zone and it as it contains tungsten-containing catalyst,retro-aldol conversion can occur prior to entry of the feed into thereaction zone. With the use of recycled hydrogenation solution, the massratio of carbohydrate to total recycled product stream and added solventis often in the range of about 0.05:1 to 0.4:1, and sometimes betweenabout 0.1:1 to 0.3:1. The recycled raw product stream is often betweenabout 20 and 80 volume percent of the product stream.

The carbohydrate contained in the carbohydrate feed is provided at arate of at least 50 or 100, and preferably, between about 150 to 500grams per liter of reactor volume per hour. Optionally, a separatereaction zone can be used that contains retro-aldol catalyst with anessential absence of hydrogenation catalyst.

The Conversion Process

In the processes, the carbohydrate feed is introduced into solvent thatcontains catalyst for the catalytic conversion and hydrogen. The solventis frequently water but can be lower alcohol or polyalcohols of 1 to 6carbons, especially methanol, ethanol, n-propanol and isopropanol.

The carbohydrate feed may or may not have been subjected to retro-aldolconditions prior to being introduced into the reaction zone, and thecarbohydrate feed may or may not have been heated through thetemperature zone of 170° C. to 230° C. upon contacting the liquid mediumin the reaction zone. Thus, in some instances the retro-aldol reactionsmay not occur until the carbohydrate feed is introduced into the liquidmedium, and in other instances, the retro-aldol reactions may have atleast partially occurred prior to the introduction of the carbohydratefeed into the liquid medium in the reaction zone. It is generallypreferred to quickly disperse the carbohydrate feed in the liquid mediumespecially where the hydrogenation medium is used to provide direct heatexchange to the carbohydrate feed. This dispersion can be achieved byany suitable procedure including, but not limited to, the use ofmechanical and stationary mixers and rapid diffusional mixing. The useof multiple ports to introduce the feed into the reactor alsofacilitates quick dispersion.

The preferred temperatures for retro-aldol reactions are typicallybetween about 230° C. and 300° C., and more preferably between about240° C. and 280° C., although retro-aldol reactions can occur at lowertemperatures, e.g., as low as 90° C. or 150° C. The pressures (absolute)are typically in the range of about 15 to 200 bar (1500 to 20,000 kPa),say, between about 25 and 150 bar (2500 and 15000 kPa). Retro-aldolreaction conditions include the presence of retro-aldol catalyst. Aretro-aldol catalyst is a catalyst that catalyzes the retro-aldolreaction. Examples of tungsten compounds that can provide retro-aldolcatalyst include, but are not limited to, heterogeneous and homogeneouscatalysts, including catalyst supported on a carrier, comprise tungstenand its oxides, sulfates, phosphides, nitrides, carbides, halides, acidsand the like. Tungsten carbide, soluble phosphotungstens, tungstenoxides supported on zirconia, alumina and alumina-silica are alsoincluded. Preferred catalysts are provided by soluble tungsten compoundsand mixtures of tungsten compounds. Soluble tungstates include, but arenot limited to, ammonium and alkali metal, e.g., sodium and potassium,paratungstate, partially neutralized tungstic acid, ammonium and alkalimetal metatungstate and ammonium and alkali metal tungstate. Often thepresence of ammonium cation results in the generation of amineby-products that are undesirable in the lower glycol product. Withoutwishing to be limited to theory, the species that exhibit the catalyticactivity may or may not be the same as the soluble tungsten compoundsintroduced as a catalyst. Rather, a catalytically active species may beformed as a result of exposure to the retro-aldol reaction conditions.Tungsten-containing complexes are typically pH dependent. For instance,a solution containing sodium tungstate at a pH greater than 7 willgenerate sodium metatungstate when the pH is lowered. The form of thecomplexed tungstate anions is generally pH dependent. The rate thatcomplexed anions formed from the condensation of tungstate anions areformed is influenced by the concentration of tungsten-containing anions.A preferred retro-aldol catalyst comprises ammonium or alkali metaltungstate that becomes partially neutralized with acid, preferably anorganic acid of 1 to 6 carbons such as, but without limitation, formicacid, acetic acid, glycolic acid, and lactic acid. The partialneutralization is often between about 25 and 75%, i.e., on averagebetween 25 and 75% of the cations of the tungstate become acid sites.The partial neutralization may occur prior to introducing thetungsten-containing compound into the reactor or with acid contained inthe reactor.

The concentration of retro-aldol catalyst used may vary widely and willdepend upon the activity of the catalyst and the other conditions of theretro-aldol reaction such as acidity, temperature and concentrations ofcarbohydrate. Typically, the retro-aldol catalyst is provided in anamount to provide between about 0.01 or 0.05 and 100, say, between about0.02 or 0.1 and 50, grams of tungsten calculated as the elemental metalper liter of aqueous, hydrogenation medium. The retro-aldol catalyst canbe added as a mixture with all or a portion of the carbohydrate feed oras a separate feed to the liquid medium or with recycling liquid mediumor any combination thereof. Where the retro-aldol catalyst comprises twoor more tungsten species and they may be fed to the reaction zoneseparately or together. In some preferred aspects, the carbohydrate feedis admixed with retro-aldol catalyst prior to contacting hydrogenationcatalyst. The admixture is preferably at a pH of greater than 4, andoften greater than 5.5, and in some instances between about 6 and 7.5,say 6.5 to 6.8.

Frequently the carbohydrate feed is subjected to retro-aldol conditionsprior to being introduced into the hydrogenation medium in the reactionzone containing hydrogenation catalyst. Preferably the introduction intothe aqueous, hydrogenation medium occurs in less than one minute, andmost often less than 10 seconds, from the commencement of subjecting thecarbohydrate feed to the retro-aldol conditions. Some, or all of theretro-aldol reaction can occur in the reaction zone containing thehydrogenation catalyst. In any event, the most preferred processes arethose having a short duration of time between the retro-aldol conversionand hydrogenation.

Under many process conditions useful in the processes of this invention,tungsten-containing precipitates can form and may be suspended ordeposited on surfaces, including the surface of the hydrogenationcatalyst where the activity of the hydrogenation catalyst can beaffected.

The hydrogenation, that is, the addition of hydrogen atoms to an organiccompound without cleaving carbon-to-carbon bonds, can be conducted at atemperature in the range of about 100° C. or 120° C. to 300° C. or more.Typically, the hydrogenation medium is maintained at a temperature of atleast about 230° C. until substantially all carbohydrate is reacted tohave the carbohydrate carbon-carbon bonds broken by the retro-aldolreaction, thereby enhancing selectivity to ethylene and propyleneglycol. Thereafter, if desired, the temperature of the hydrogenationmedium can be reduced. However, the hydrogenation proceeds rapidly atthese higher temperatures. Thus, the temperatures for hydrogenationreactions are frequently between about 230° C. and 300° C., say, betweenabout 240° C. and 280° C. Typically, in the retro-aldol process thepressures (absolute) are typically in the range of about 15 to 200 bar(1500 to 20,000 kPa), say, between about 25 and 150 bar (2500 and 15000kPa). The hydrogenation reactions require the presence of hydrogen aswell as hydrogenation catalyst. Hydrogen has low solubility in aqueoussolutions. The concentration of hydrogen in the aqueous, hydrogenationmedium is increased with increased partial pressure of hydrogen in thereaction zone. The pH of the aqueous, hydrogenation medium is often atleast about 2.5 or 3, say, between about 3 or 3.5 and 8, and in someinstances between about 3.5 or 4 and 7.5.

The hydrogenation is conducted in the presence of a hydrogenationcatalyst. Frequently the hydrogenation catalyst is a supported,heterogeneous catalyst. It can be deployed in any suitable manner,including, but not limited to, fixed bed, fluidized bed, trickle bed,moving bed, slurry bed, loop bed, such as Buss Loop® reactors availablefrom BUSS ChemTech AG, and structured bed. One type of reactor that canprovide high hydrogen concentrations and rapid heating is cavitationreactor such as disclosed in U.S. Pat. No. 8,981,135 B2, hereinincorporated by reference in its entirely. Cavitation reactors generateheat in localized regions and thus the temperature in these localizedregions rather the bulk temperature of the liquid medium in the reactionzone is the temperature process parameter for purposes of thisinvention. Cavitation reactors are of interest for this process sincethe retro-aldol conversion can be very rapid at the temperatures thatcan be achieved in the cavitation reactor.

Nickel, ruthenium, palladium and platinum are among the more widely usedreducing metal catalysts. However, many reducing catalysts will work inthis application. The catalysts may be supported or unsupported such asRaney nickel. The reducing catalyst can be chosen from a wide variety ofsupported transition metal catalysts. One particularly favored catalystfor the reducing catalyst in this process is a supported, Ni-Recatalyst. A similar version of Ni/Re or Ni/Ir can be used with goodselectivity for the conversion of the formed glycolaldehyde to ethyleneglycol. Nickel-rhenium is a preferred reducing metal catalyst and may besupported on alumina, alumina-silica, silica or other supports.Supported Ni-Re catalysts with B as a promoter are useful. Generally,for slurry reactors, a supported hydrogenation catalyst is provided inan amount of less than 10, and sometimes less than about 5, say, about0.1 or 0.5 to 3, grams per liter of nickel (calculated as elementalnickel) per liter of liquid medium in the reactor. As stated above, notall the nickel in the catalyst is in the zero-valence state, nor is allthe nickel in the zero-valence state readily accessible by glycolaldehyde or hydrogen. Hence, for a particular hydrogenation catalyst,the optimal mass of nickel per liter of liquid medium will vary. Forinstance, Raney nickel catalysts would provide a much greaterconcentration of nickel per liter of liquid medium. Frequently in aslurry reactor, the hydrogenation catalyst is provided in an amount ofat least about 5 or 10, and more often, between about 10 and 70 or 100,grams per liter of aqueous, hydrogenation medium and in a packed bedreactor the hydrogenation catalyst comprises about 20 to 80 volumepercent of the reactor. In some instances, the weight hourly spacevelocity is between about 0.01 or 0.05 and 1 hr⁻¹ based upon totalcarbohydrate in the feed. Preferably the residence time is sufficientthat glycol aldehyde and glucose are less than 0.1 mass percent of thereaction product, and most preferably are less than 0.001 mass percentof the reaction product.

The carbohydrate feed is at least 50 grams of carbohydrate per liter perhour, and is often in the range of about 100 to 700 or 1000, grams ofcarbohydrate per liter per hour.

In the processes of this invention, the combination of reactionconditions (e.g., temperature, hydrogen partial pressure, concentrationof catalysts, hydraulic distribution, and residence time) are sufficientto convert at least about 95, often at least about 98 or 99, masspercent and sometimes essentially all of the carbohydrate that yieldsaldose or ketose. It is well within the skill of the artisan having thebenefit of the disclosure herein to determine the set or sets ofconditions that will provide the sought conversion of the carbohydrate.

Ion Exclusion Chromatographic Separation

Ion exclusion chromatographic separation is used in the processes ofthis invention to obtain as the sought product, a producer compositionrich in dissolved tungsten compound, and reject lower glycol and higherboiling coproducts which are recovered in a subsequent eluant. Theproducer composition has a substantially reduced ratio of lower glycoland higher boiling coproducts to the tungsten compounds as compared tothat ratio in the retained liquid phase. Accordingly, recovery of thetungsten compounds can be undertaken without significant loss of lowerglycol and higher boiling coproducts, and the subsequent eluant can bepurged and/or treated without the undue loss of tungsten compounds.

The feed to the ionic resin for the ion exclusion chromatographicseparation is at least a portion, which may be an aliquot or aliquantportion, of the retained liquid phase from the separation of lowerglycol from the reaction product. Any suitable unit operation oroperations can be used to separate lower glycol including, but notlimited to, chromatographic separation, sorption, membrane separation,flash separation, distillation, rectification, and evaporation. Vaporliquid separations are typically used. In some instances, the withdrawnreaction product is depressurized with the gases being captured forrecovery of the hydrogen and removal of unwanted gaseous by-productssuch as methane and carbon dioxide. A vapor/liquid separation thenprovides a vaporous overhead containing at least a portion of the lowerglycol and other volatilized compounds such as acetic acid. The retainedliquid phase often contains lower glycol in addition to the higherboiling point coproducts and tungsten compounds. Where a distillation,flash or evaporation is used, the bottoms temperature is frequently inthe range of about 120° C. to 200° C., and the vapor phase is at apressure of between about 500 to 10,000, say, 1000 to 5000, kPaabsolute. As most of the water and total ethylene glycol and propyleneglycol are passed to the vapor phase in these embodiments of thisinvention, the liquid phase may sometimes be rich in heavies and thusincrease the difficulties in processing. Accordingly, water ispreferably added to the liquid phase from the vapor/liquid separator toprovide a liquid comprising at least about 25, and sometimes at leastabout 35, mass percent water.

The composition of the retained liquid phase will depend upon, amongother things, the unit operations used to separate lower glycol and theextent that these unit operations are used to remove lower glycol; theconversion process operation and reaction product composition; theconcentration of tungsten compounds in the reaction products and whetherwater or other solvent is added to the retained liquid phase, and if so,how much. In most instances, lower glycol will be the most prevalentorganic species in the retained liquid phase, and the retained liquidphase will also contain higher boiling coproducts, i.e, sorbitol,erythritol, threitol, and glycerin, and potentially carboxylic acids oresters. The retained liquid phase will also contain tungsten compounds.The tungsten compounds include soluble tungsten compounds and mayinclude solid tungsten compounds such as tungsten bronzes and tungsticacid. The tungsten compounds are typically oxygenated tungsten anionssuch as tungstic acid, partially neutralized tungstic acid, tungstate,metatungstate, paratungstate, and the like, and may or may not havecatalytic activity. One or more unit operations can occur to theretained liquid phase that can change its composition such as theaddition of water or other solvent, or further vapor/liquid separationor sorption or chemical reaction.

The processes of this invention may be used with retained liquid phasesthat vary widely in the concentration of lower glycol as both ethyleneglycol and propylene glycol elute from the ion exclusion chromatographyafter most of the tungsten compound have been eluted. Accordingly, lowerglycol may comprise as much as about 50 or 60, say, between about 10 and50, mass percent of the organics in the retained liquid phase. As littleof the higher boiling coproducts are separated with lower glycol fromthe reaction product, a ratio of the mass of higher boiling coproductsto tungsten compounds (calculated as the metal) is useful to describethe chromatographic separation. In most instances this ratio is greaterthan about 4:1, and can be up to about 300:1 or 500:1, and in someinstances between about 25:1 to 100:1.

All, or an aliquot or aliquant portion of, the retained liquid phase canbe contacted with the ionic resin for the ion exclusion chromatographicseparation. The contact may be continuous, semi-continuous, intermittentor batch. The retained liquid phase may be diluted, e.g., with water todecrease viscosity. Sometimes the viscosity at the temperature ofcontact with the ionic resin is less than about 100 Pascal seconds, andin some instances between about 0.1 and 50 Pascal seconds. Thetemperature of the retained liquid phase contacting the ionic resin isbelow that which adversely affects the resin, and is often in the rangeof about 0° C. to 150° C., say, between about 10° C. and 100° C. Thepressure of the feed can fall within a wide range, e.g., from about 100to 100,000 kPa absolute. The liquid hourly space velocity of the feed tothe ionic resin will depend, upon other things, the nature of the feedand its composition, the sought degree of chromatographic separation;the nature of the ionic resin; and the design of the equipment used forthe ion exclusion chromatography. Frequently, the liquid hourly spacevelocity is in the range of about 0.1 to 50 hr⁻¹.

The contact with the ionic resin can be in a moving or fixed bed, andcan be in a batch, semi-continuous or continuous mode of operation. Theionic resin is typically packed in a column, and the feed is passedthrough the column to provide an eluate. Solvent is then passed throughthe column to elute other components in the feed. The determination ofthe diameter and height of the columns is well within the skill of theordinary artisan in the field of ion exclusion chromatographicseparations having the benefit of the disclosure herein. In someinstances, the processes of this invention use a simulated moving bed(SMB). An SMB apparatus can, if desired, operate continuously. An SMBapparatus comprises multiple columns containing ionic resin connected inseries. The valve and column arrangement is such that the points ofaddition of feed and solvent and the points of withdrawal of the desiredproduct rich in tungsten compound (the producer composition) and theorganic product, in the series of columns, are periodically moved fromcolumn to column. The movement is counter to the flow of liquid in theseries of columns so as to give the impression of a moving bed. For ageneral discussion of SMB, see, for instance, U.S. Pa. Nos. 2,985,589;4,340,724; and 6,479,716.

Any suitable, ionic resin can be used including strong and weak anionicresins and strong and weak cationic resins. The resins can be gel or,preferably, macroreticular resins. In some instances, the resins have adegree of crosslinking of at least about 3, say, up to about 15 or more,percent. Frequently resins having a degree of cross linking of at leastabout 6, preferably at least about 8, percent are used to enhancestability and to provide more porosity. In some instances, the porosityis such that the organics are eluted without using undue amounts ofsolvents. In these instances, the focus of the chromatographicseparation is on achieving the sought tungsten compound containingeluant, and there is no desire to use the chromatographic separation forseparation of the various organics. The effectiveness of an ionic resinfor separation of the tungsten-containing fraction from the organics canbe perceived by comparing the total excluded volume with the totalincluded volume. In general, the greater the differences, the moreeffective the separation. Total excluded volume is the amount of solventrequired to exclude an aliquot of an ionic compound on the resin such astungstate. The total included volume is the amount of solvent requiredto elute an aliquot of a non-ionic compound such as glycerin.

Many commercially-available ionic resins comprise one of polystyrene,polymethacrylate and polyacrylate, and often are cross linked using anagent such as divinyl benzene. The ionic functionality can be provided,in the case of anionic resins, amines and in the case of cationicresins, carboxylic, phosphonic or sulfonic groups. In some instances,the size of the ionic resin particles is in the range of 100 to 10,000or more microns in major dimension. The preferred ionic resins aremacroreticular cationic resins having carboxylic or sulfonicfunctionality due to the stability of the resins. Preferably, the cationassociated with the fresh cationic resin is not one that formsprecipitates with the tungsten compound, although, after multiplecycles, any cation that forms precipitate would be eluted. Sodiumcationic resins are preferred. In some instance the cationic resin is apolystyrene sulfonate strong cation exchange resin with a degree ofcross-linking of at least about 4, say, at least about 6, e.g., betweenabout 6 and 15, percent.

Drawings

Reference is made to the drawing which is provided to facilitate theunderstanding invention but is not intended to be in limitation of theinvention. The drawing omits minor equipment such as pumps, compressors,valves, instruments, heat exchangers and other devices the placement ofwhich and operation thereof are well known to those practiced inchemical engineering. The drawing also omits ancillary unit operations.

With reference to FIG. 1 , apparatus 100 comprises catalytic conversionreactor 102 for the conversion of carbohydrate to ethylene glycol and/orpropylene glycol. The reactor may be a single vessel or two or morevessels of the same or different design in parallel or in series. Atleast one vessel contains heterogeneous hydrogenation catalyst. At leastone vessel contains retro-aldol catalyst, especially soluble retro-aldolcatalyst.

As shown, carbohydrate feed is passed via line 104 to reactor 102, andhydrogen for the catalytic conversion is passed to reactor 102 via line106. Tungsten compound for the retro aldol catalyst is provided at leastby lines 110 and 112 as will be discussed later. A reaction product iswithdrawn from reactor 102 via line 108.

The reaction product contains one or both of ethylene glycol andpropylene glycol, and it contains higher boiling coproducts (sorbitol,erythritol, threitol, glycerol, and 1,2-butanediol). Since the catalyticconversion is conducted at elevated pressure in the presence ofhydrogen, the reaction product contains dissolved hydrogen and dissolvedtungsten compound.

As depicted, the reaction product is passed to vapor/liquid separator114. The vapor/liquid separator may comprise one or more unitoperations, e.g., with recovery of hydrogen and light gases followed byone or more unit operations to recover water and ethylene glycol andpropylene glycol from the reaction product. Hydrogen and other lightgases such as carbon dioxide and methane, are withdrawn via line 116 forrecovery of hydrogen for recycle. The liquid components can then besubjected to one or more unit operations to recover lower glycolincluding additional vapor/liquid separations or liquid/liquidseparations such as selective membrane permeation and selectivesorption. In another mode, the vapor/liquid separation provides avaporous overhead that contains a substantial portion of the ethyleneglycol and propylene glycol in the reaction product. Often, at leastabout 30, and more frequently at least about 50, say, about 50 to 75 or95, mass percent of the total ethylene glycol and propylene glycol areprovided to the overhead. The overhead in line 118 would be passed tounit operations for the refining of ethylene glycol and propylene glycolas well as separation of normally gaseous components not removed withthe hydrogen and light gases.

All or a portion (aliquot or aliquant) of the retained liquid phase iswithdrawn from vapor/liquid separator 114 via line 120. Shown is anembodiment where higher boiling components in the retained liquid issubjected to catalytic conditions to convert at least a portion of thehigher boiling coproducts to lower glycol, e.g., by hydrogenolysis. Aportion of the retained liquid phase can be drawn off of line 120 byline 122 for such catalytic processing even though it contains tungstencompound. In this manner, the volume of retained liquid phase beingsubjected to ion exclusion chromatography can be controlled, especiallyas plant production is varied. As discussed later, the organic phasefrom ion exclusion chromatography can also be subjected to suchcatalytic processing.

All or the remaining portion of the retained liquid phase in line 120 ispassed to a simulated moving bed unit 124 for ionic exclusionchromatography to provide a separated tungsten compound-containingeluted phase and a separated organic-containing eluted phase. Ifdesired, the portion of the retained liquid phase may be subjected tochemical and/or physical unit operations to reduce the presence ofsolids, e.g., filtration, oxidation, or the like.

For purposes of discussion and not in limitation of the invention, thesimulated moving bed contains ten columns of strong cationic resin inseries with valving to add and withdraw liquid from each column. Avolume of retained liquid phase is introduced over a predetermined timeinto one of the series of columns, and liquid that passes through thatcolumn is passed to the next column in the series and so on for all tencolumns. After the predetermined time, the feed of retained liquid phaseis passed to the previous column in the series. This sequencing isrepeated continuously. A tungsten-containing eluted phase is withdrawnfrom a column later in the direction of the flow of the liquid, say,from the fourth column from the column in which the retained liquidphase is introduced. The selection of the column is well within theskill of the art of ion exclusion chromatography in simulated movingbeds and will depend, in part, upon the portion of the tungsten compoundto be recovered and the concentration of organics that can be toleratedin the tungsten compound-containing eluted phase. The ion exclusionchromatography can be operated such that higher percentages of thetungsten compound going to the tungsten compound-containing elutedphase, e.g., at least about 90, and preferably at least about 95 or 99,atomic percent of the tungsten. Alternatively, the ion exclusionchromatography can be operated such that the tungsten-containing elutedphase Contamination with organic compound is usually not as critical,however, especially where the tungsten compound-containing eluted phaseis subjected to pH adjustment, e.g., to convert tungsten complexes topartially neutralized tungstate, minimization of organic acids ispreferred to reduce the amount of base required for the pH adjustment.Frequently, the mass ratio of total organics to tungsten compound(calculated as the element) is less than about 10:1, and in someinstances less than about 1:1, say, about 0.1:1. The tungstencompound-containing eluted phase is withdrawn from the simulated movingbed 124 via line 126. If desired, a portion of the eluted phase can bewithdrawn from line 126 via line 128 for purge or recovery of tungsten.

The relative volume of the purge stream will depend upon, among otherthings, the portion of the tungsten species that are renderedcatalytically inactive or relatively inactive during the reactionprocesses such as tungstic acid or tungsten bronzes. The purge can becontinuous or intermittent. In instances where a purge is used, oftenbetween about 5 and 40, say, between about 10 and 25, mass percent ofthe eluted phase is purged. Tungsten can be recovered from the purgestream. Any suitable process or combination of processes can be used torecover the tungsten including, but not limited to, ion exchange andacidification to precipitate tungstic acid for separation.

All or a portion of the tungsten compound-containing eluted phase can bepassed continuously or intermittently via line 126 to treatment vessel130. As the tungsten compound containing eluted phase may contain anumber of tungsten compounds, including, but not limited to, meta- andpara-tungstates, tungstic acid, and partially neutralized tungstate,conversion of the species to partially neutralized tungstate facilitatesproviding more predictable retro-aldol catalytic activity for therecycled tungsten compound. As shown, base such as sodium hydroxide, isadded to treatment vessel 130 via line 132 in an amount sufficient toadjust the pH to between about 6 and 8, and frequently between about 6.5and 6.8. The treated effluent is withdrawn from vessel 130 via line 134for recycle to reactor 102.

Returning to line 126, if desired, all or a portion of the tungstencompound-containing eluted phase can be directed continuously orintermittently to line 136 for recycle to reactor 102 and bypassingtreatment vessel 130. Where bypassing does occur, typically betweenabout 20 to 100, and sometimes between about 25 and 80, mass percent ofthe tungsten compound-containing eluted phase is passed from line 126 toline 136. In some instances, the bypass tungsten compound-containingeluted phase is such that the pH of the mixture of feed, organic recycleand retro-aldol catalyst in line 104 is at least about 4.5, preferablyat least about 5, say, 5.5 to 8, and sometimes between about 5.5 and6.8.

The treated effluent in line 134 from treatment vessel 130 is depictedas being combined with any bypass in line 136 for recycle to reactor102. All or a portion of the recycled tungsten compound in line 136 canbe directed via line 112 to line 104 for admixing with feed, of all or aportion of the recycled tungsten compound in line 136 can be passed vialine 138 directly into reactor 102. In instances where the recycledtungsten compound is added directly to reactor 102, it is especiallybeneficial if it has passed through treatment vessel 130 and has a pH inthe higher range, e.g., between about 6.5 and 8, such that it can beused in part to control pH in the reactor.

Returning to simulated moving bed 124, a solvent, such as water, isadded via line 125 at the fifth column to elute organics from thesorption media in simulated moving bed 124 to provide an eluantcontaining organics at the last column in the series. By the simulatedmoving bed sequencing, the organic eluant is withdrawn via line 140. Aportion of this eluant is typically purged via line 142 to assure steadystate operating compositions in reactor 102. The purge is often in therange of 1 to 30 mass percent of the eluant, the greater percentagesfrequently being used when a significant portion of the retained liquidphase is bypassed via line 122. All or a portion of the organic eluantand bypassing retained liquid phase can be passed directly to reactor102, or as shown, subjected to a unit operation to enhance theconversion efficiency of the feed to monoethylene glycol. In thedrawing, the organic eluant in line 140 is combined with any retainedliquid phase in line 122 and passed to hydrogenolysis reactor. Inhydrogenolysis reactor 144, hydrogen supplied via line 150 andhydrogenolysis catalyst are contacted with the organics supplied by line122 under hydrogenolysis conditions to provide a hydrogenolysis productcontaining, among other things, monoethylene glycol and propylene glycoland a reduced concentration of carboxylic acids and higher boiling pointcoproducts. It should be understood that the hydrogen for thehydrogenolysis can be off gases withdrawn from reactor 102 via line 150.Hydrogenolysis conditions often include a temperature of between about150° C. or 200° C. and 240° C., preferably between about 200° C. and230° C.; a hydrogen partial pressure of between about 2500 to 12,000,say, about 5000 to 10,000, kPa, and a liquid hourly space velocity ofbetween about 0.01 to 20 hr⁻¹. Any suitable hydrogenolysis catalyst canbe used such as those containing one or more of nickel, cobalt,ruthenium, rhodium, platinum, and palladium. For the sake ofconvenience, the hydrogenolysis catalyst can be the Hcat used for thehydrogenation.

Hydrogenolysis product is withdrawn from hydrogenolysis reactor 144 vialine 146 and gases are withdrawn via line 148 for recovery andpurification. All or a portion of the hydrogenolysis product in line 146can be passed to line 108 for recovery of ethylene glycol and propyleneglycol in vapor/liquid separator 114.

It is claimed:
 1. A catalytic process for producing a lower glycolcomprising at least one of ethylene glycol and propylene glycol from acarbohydrate-containing feed that comprises at least one of aldose- andketose-yielding carbohydrate, said process comprising: (a) continuouslyor intermittently supplying the feed to a reaction zone having thereindissolved tungsten compounds at least one of which is homogeneous,tungsten-containing retro-aldol catalyst and at least one heterogeneoushydrogenation catalyst, said liquid medium being at catalytic conversionconditions including the presence of dissolved hydrogen, to produce areaction product containing said lower glycol and one or more higherboiling point coproducts comprising sorbitol, erythritol, threitol andglycerin; (b) continuously or intermittently withdrawing liquid mediumthat contains reaction product and dissolved tungsten compounds from thereaction zone; (c) subjecting at least a portion of the withdrawn liquidmedium to one or more unit operations to remove at least a portion ofthe lower glycol in a separated fraction and provide a retained liquidphase containing dissolved tungsten compounds and higher boiling pointcoproducts with a mass ratio of higher boiling coproducts to tungstencompounds calculated as the metal of greater than about 4:1; and (d)contacting at least a portion of the retained liquid phase with an ionicresin for ion exclusion chromatography, to provide a first elutedfraction containing dissolved tungsten compounds and a mass ratio ofhigher boiling coproducts to tungsten compounds calculated as the metalof less than about 1:1, and contacting the ionic resin with sufficientsolvent to provide at least one subsequent eluted fraction containingone or more higher boiling point coproducts and a lower concentration oftungsten compounds than that in the retained liquid phase.
 2. Theprocess of claim 1 wherein at least about 90 mass percent of thetungsten compounds contained in the retained liquid phase contacted withthe ionic resin are in the first eluted fraction.
 3. The process ofclaim 1 wherein the portion of the retained liquid phase contacted withthe cationic resin is a purge stream.
 4. The process of claim 1 whereinat least a portion of the first eluted fraction is recycled to step (a).5. The process of claim 4 wherein the pH of the recycled, first elutedfraction is provided at between about 6.5 and 8 before being passed tostep (a).
 6. The process of claim 5 wherein at least a portion of thetungsten compounds in the recycled, first eluted fraction is halfneutralized tungstic acid.
 7. The process of claim 1 wherein at least aportion of the at least one subsequently eluted fraction containing oneor more higher boiling point coproducts is subjected to hydrogenolysisconditions to provide at least one of ethylene glycol and propyleneglycol.
 8. The process of claim 1 wherein the ionic resin comprisescationic resin.
 9. The process of claim 8 wherein the cationic resincomprises polystyrene sulfonate strong cation exchange resin.
 10. Theprocess of claim 1 wherein the ionic resin has a degree of crosslinkingof at least 6 percent.
 11. The process of claim 10 wherein the ionicresin has a degree of crosslinking of at least 8 percent.
 12. Theprocess of claim 1 wherein step (d) is conducted as a simulated movingbed.
 13. The process of claim 1 wherein the one or more unit operationsof step (c) comprise a vapor liquid separation.
 14. A producercomposition of matter comprising dissolved tungsten compound and one ormore higher boiling point polyols comprising sorbitol, erythritol,threitol and glycerin wherein the mass ratio of total higher boilingpolyol to tungsten compounds calculated as the metal is less than about5:1.
 15. The producer composition of claim 14 wherein the mass ratio oftotal higher boiling polyol to tungsten compounds calculated as themetal is between about 0.01:1 and 1:1.